Increased plasma nitrate concentrations from dietary sources of nitrate have proven to benefit exercise performance. Beetroot (BR) contains relatively high levels of nitrate (NO3 −), which increases nitric oxide stores. This study investigated whether dietary nitrate supplementation, in the form of a BR beverage, would improve rowing performance during ergometer repetitions. In a randomized crossover design, 14 well-trained junior male rowers consumed 500 ml of either BR or placebo (PL) daily for 6 d. After supplementation, rowers completed 6 maximal 500-m ergometer repetitions and times were recorded. A 7-d washout period separated the 2 trials. Blood pressure, oxygen saturation, maximum heart rate, urine (specific gravity, pH, and nitrites), and lactates were collected for analysis at baseline and pre- and postperformance. Changes in the mean with 95% confidence limits were calculated. There was a likely benefit to average repetition time in the BR condition, compared with PL (0.4%, 95% confidence limits, ± 1.0%). In particular, Repetitions 4–6 showed an almost certain benefit in rowing time on BR (1.7%, 95% CL, ± 1.0%). The underlying mechanism for the observed results remains unknown, as differences observed in rowers’ physiological measures between the 2 conditions were unclear. Conclusively, nitrate supplementation in the form of BR juice resulted in improved maximal rowing-ergometer repetitions, particularly in the later stages of exercise.
Hannah Bond, Lillian Morton and Andrea J. Braakhuis
Lawrence E. Armstrong, Amy C. Pumerantz, Melissa W. Roti, Daniel A. Judelson, Greig Watson, Joao C. Dias, Bülent Sökmen, Douglas J. Casa, Carl M. Maresh, Harris Lieberman and Mark Kellogg
This investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean ± standard deviation; age, 21.6 ± 3.3 y) consumed 3 mg caffeine · kg−1 · d−1 on days 1 to 6 (equilibration phase). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n = 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine · kg−1 · d−1 in capsules, with no other dietary caffeine intake. The following variables were unaffected (P > 0.05) by different caffeine doses on days 1, 3, 6, 9, and 11 and were within normal clinical ranges: body mass, urineosmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. Therefore, C0, C3, and C6 exhibited no evidence of hypohydration. These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic.
Nora R. Decher, Douglas J. Casa, Susan W. Yeargin, Matthew S. Ganio, Michelle L. Levreault, Catie L. Dann, Camille T. James, Megan A. McCaffrey, Caitlin B. O’Connor and Scott W. Brown
To assess the hydration status and level of hydration knowledge of youths at summer sports camps.
Sixty-seven active youths, 57 males (mean ± SD, 12 ± 2 y, 136 ± 16 cm, 50.6 ± 21.1 kg) and 10 females (13 ± 2 y, 153 ± 8 cm, 45.2 ± 9.0 kg) participated in 4 d of sports camp. Hydration status was assessed before the first practice (AM) and after the second practice (PM). Participants completed suriveys assessing hydration knowledge (HAQ) and hydration habits on day 3 and a self-assessment (EQ#1).
Mean AM urine specific gravity (USG) and urine osmolality (Uosm) scores ranged from minimal to significant dehydration across 4 d, even when temperatures were mild. Correlations between hydration indices and EQ#1, ranging from 0.11 to −0.51, were statistically significant (P < .05), indicating that subjects recognized when they were doing a good or bad job hydrating. HAQ did not correlate strongly with hydration indices suggesting other impediments to hydration. Thirst correlated negatively with EQ#1 (from −0.29 to −0.60).
Hydration at summer sports camp is a concern and special efforts need to be made to help youths develop hydration strategies.
Lawrence E. Armstrong, Carl M. Maresh, John W. Castellani, Michael F. Bergeron, Robert W. Kenefick, Kent E. LaGasse and Deborah Riebe
Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color (
Stefan Pettersson and Christina M. Berg
Weight category athletes are known for practicing rapid weight loss before competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the current study was to assess prevalence of hypohydration at competition time among elite athletes’ in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day’s first morning urine sample. Hypohydration was defined as USG ≥1.020 and serious hypohydration as USG > 1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favorable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration before competition.
J.D. Adams, Stavros A. Kavouras, Evan C. Johnson, Lisa T. Jansen, Catalina Capitan-Jimenez, Joseph I. Robillard and Andy Mauromoustakos
The purpose of this investigation was to quantify the effects of storage temperature, duration, and the urinary sediment on urinary hydration markers. Thirty-six human urine samples were analyzed fresh and then the remaining sample was separated into 24 separate vials, six in each of the following four temperatures: 22 °C, 7 °C, -20 °C, and -80 °C. Two of each sample stored in any given temperature, were analyzed after 1, 2, and 7 days either following vortexing or centrifugation. Each urine sample was analyzed for osmolality (UOsm), urine specific gravity (USG), and urine color (UC). UOsm was stable at 22 °C, for 1 day (+5–9 mmol∙kg-1, p > .05) and at 7 °C, UOsm up to 7 days (+8–8 mmol∙kg-1, p > .05). At -20 and -80 °C, UOsm decreased after 1, 2, and 7 days (9–61 mmol∙kg-1, p < .05). Vortexing the sample before analysis further decreased only UOsm in the -20 °C and -80 °C storage. USG remained stable up to 7 days when samples were stored in 22 °C or 7 °C (p > .05) but declined significantly when stored in -20 °C, and -80 °C (p < .001). UC was not stable in any of the storing conditions for 1, 2, and 7 days. In conclusion, these data indicate that urine specimens analyzed for UOsm or USG remained stable in refrigerated (7 °C) environment for up to 7 days, and in room temperature for 1 day. However, freezing (-20 and -80 °C) samples significantly decreased the values of hydration markers.
Ben Desbrow, Katelyn Barnes, Caroline Young, Greg R. Cox and Chris Irwin
Immediate postexercise access to fruit/fluid via a recovery “station” is a common feature of mass participation sporting events. Yet little evidence exists examining their impact on subsequent dietary intake. The aim of this study was to determine if access to fruit/water/sports drinks within a recovery station significantly alters dietary and fluid intakes in the immediate postexercise period and influences hydration status the next morning. 127 (79 males) healthy participants (M ± SD, age = 22.5 ± 3.5y, body mass (BM) = 73 ± 13kg) completed two self-paced morning 10km runs separated by 1 week. Immediately following the first run, participants were randomly assigned to enter (or not) the recovery station for 30min. All participants completed the alternate recovery option the following week. Participants recorded BM before and after exercise and measured Urine Specific Gravity (USG) before running and again the following morning. For both trial days, participants also completed 24h food and fluid records via a food diary that included photographs. Paired-sample t tests were used to assess differences in hydration and dietary outcome variables (Recovery vs. No Recovery). No difference in preexercise USG or BM change from exercise were observed between treatments (p’s > .05). Attending the recovery zone resulted in a greater total daily fluid (Recovery = 3.37 ± 1.46L, No Recovery = 3.16 ± 1.32L, p = .009) and fruit intake (Recovery = 2.37 ± 1.76 servings, No Recovery = 1.55 ± 1.61 servings, p > .001), but had no influence on daily total energy (Recovery = 10.15 ± 4.2MJ, No Recovery = 10.15 ± 3.9MJ), or macronutrient intakes (p > .05). Next morning USG values were not different between treatments (Recovery = 1.018 ± 0.007, No Recovery = 1.019 ± 0.009, p > .05). Recovery stations provide an opportunity to modify dietary intake which promote positive lifestyle behaviors in recreational athletes.
Bjoern Geesmann, Joachim Mester and Karsten Koehler
Athletes competing in ultra-endurance events are advised to meet energy requirements, to supply appropriate amounts of carbohydrates (CHO), and to be adequately hydrated before and during exercise. In practice, these recommendations may not be followed because of satiety, gastrointestinal discomfort, and fatigue. The purpose of the study was to assess energy balance, macronutrient intake and hydration status before and during a 1,230-km bike marathon. A group of 14 well-trained participants (VO2max: 63.2 ± 3.3 ml/kg/min) completed the marathon after 42:47 hr. Ad libitum food and fluid intake were monitored throughout the event. Energy expenditure (EE) was derived from power output and urine and blood markers were collected before the start, after 310, 618, and 921 km, after the finish, and 12 hr after the finish. Energy intake (EI; 19,749 ± 4,502 kcal) was lower than EE (25,303 ± 2,436 kcal) in 12 of 14 athletes. EI and CHO intake (average: 57.1 ± 17.7 g/hr) decreased significantly after km 618 (p < .05). Participants ingested on average 392 ± 85 ml/hr of fluid, but fluid intake decreased after km 618 (p < .05). Hydration appeared suboptimal before the start (urine specific gravity: 1.022 ± 0.010 g/ml) but did not change significantly throughout the event. The results show that participants failed to maintain in energy balance and that CHO and fluid intake dropped below recommended values during the second half of the bike marathon. Individual strategies to overcome satiety and fatigue may be necessary to improve eating and drinking behavior during prolonged ultra-endurance exercise.
Giannis Arnaoutis, Stavros A. Kavouras, Yiannis P. Kotsis, Yiannis E. Tsekouras, Michalis Makrillos and Costas N. Bardis
There is a lack of studies concerning hydration status of young athletes exercising in the heat.
To assess preexercise hydration status in young soccer players during a summer sports camp and to evaluate bodywater balance after soccer training sessions.
Initial hydration status was assessed in 107 young male soccer players (age 11–16 yr) during the 2nd day of the camp. Seventy-two athletes agreed to be monitored during 2 more training sessions (3rd and 5th days of the camp) to calculate dehydration via changes in body weight, while water drinking was allowed ad libitum. Hydration status was assessed via urine specific gravity (USG), urine color, and changes in total body weight. Mean environmental temperature and humidity were 27.2 ± 2 °C and 57% ± 9%, respectively.
According to USG values, 95 of 107 of the players were hypohydrated (USG ≥ 1.020) before practice. The prevalence of dehydration observed was maintained on both days, with 95.8% and 97.2% of the players being dehydrated after the training sessions on the 3rd and 5th days, respectively. Despite fluid availability, 54 of the 66 (81.8%) dehydrated players reduced their body weight (–0.35 ± 0.04 kg) as a response to training, while 74.6% (47 out of the 63) further reduced their body weight (–0.22 ± 0.03 kg) after training on the 5th day.
Approximately 90% of the young soccer players who began exercising under warm weather conditions were hypohydrated, while drinking ad libitum during practice did not prevent further dehydration in already dehydrated players.
Khaled Trabelsi, Kais el Abed, Stephen R. Stannard, Kamel Jammoussi, Khaled M. Zeghal and Ahmed Hakim
The aim of this study was to evaluate the effects of aerobic training in a fasted versus a fed state during Ramadan on body composition and metabolic parameters in physically active men. Nineteen men were allocated to 2 groups: 10 practicing aerobic training in a fasted state (FAST) and 9 training in an acutely fed state (FED) during Ramadan. All subjects visited the laboratory for a total of 4 sessions on the following occasions: 3 days before Ramadan (Bef-R), the 15th day of Ramadan; the 29th day of Ramadan (End-R), and 21 days after Ramadan. During each session, subjects underwent anthropometric measurement, completed a dietary questionnaire, and provided fasting blood and urine samples. Body weight decreased in FAST and FED by 1.9% (p < .001) and 2.6% (p = .046), respectively. Body fat percentage decreased only in FAST by 6.2% (p = .016). FAST experienced an increase in the following parameters from Bef-R to End-R: urine specific gravity (0.64%, p = .012), urea (8.7%, p < .001), creatinine (7.5%, p < .001), uric acid (12.7%, p < .001), sodium (1.9%, p = .003), chloride (2.6%, p < .001), and high-density lipoprotein cholesterol (27.3%, p < .001). Of these parameters, only creatinine increased (5.8%, p = .004) in FED. Creatinine clearance values of FAST decreased by 8.9% (p < .001) and by 7.6% in FED (p = .01) from Bef-R to End-R. The authors conclude that aerobic training in a fasted state lowers body weight and body fat percentage. In contrast, fed aerobic training decreases only body weight. In addition, Ramadan fasting induced change in some metabolic parameters in FAST, but these changes were absent in FED.